Area of survey. The boundary of the observed region in this work is indicated by the thick solid lines; the areas shaded in gray indicate the regions observed by the narrowband spectrometer (see § 2). Overlaid is the velocity‐integrated intensity distribution of CO of the first survey, whose boundary is shown by the dashed line (Fukui et al. 1999; Mizuno et al. 2001b). The contours are at the 5 σ noise level (3 K km s⁻¹) of the velocity‐integrated intensity of the first survey, showing that the present survey covers the entire region where CO emission was detected. The ellipse illustrates the position of the bar.